.TH std::mbrtowc 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::mbrtowc \- std::mbrtowc

.SH Synopsis
   Defined in header <cwchar>
   std::size_t mbrtowc( wchar_t* pwc,

                        const char* s,
                        std::size_t n,

                        std::mbstate_t* ps );

   Converts a narrow multibyte character to a wide character.

   If s is not a null pointer, inspects at most n bytes of the multibyte character
   string, beginning with the byte pointed to by s to determine the number of bytes
   necessary to complete the next multibyte character (including any shift sequences).
   If the function determines that the next multibyte character in s is complete and
   valid, converts it to the corresponding wide character and stores it in *pwc (if pwc
   is not null).

   If s is a null pointer, the values of n and pwc are ignored and call is equivalent
   to std::mbrtowc(nullptr, "", 1, ps).

   If the wide character produced is the null character, the conversion state stored in
   *ps is the initial shift state.

.SH Parameters

   pwc - pointer to the location where the resulting wide character will be written
   s   - pointer to the multibyte character string used as input
   n   - limit on the number of bytes in s that can be examined
   ps  - pointer to the conversion state used when interpreting the multibyte string

.SH Return value

   The first of the following that applies:

     * 0 if the character converted from s (and stored in pwc if non-null) was the null
       character.
     * the number of bytes [1...n] of the multibyte character successfully converted
       from s.
     * static_cast<std::size_t>(-2) if the next n bytes constitute an incomplete, but
       so far valid, multibyte character. Nothing is written to *pwc.
     * static_cast<std::size_t>(-1) if encoding error occurs. Nothing is written to
       *pwc, the value EILSEQ is stored in errno and the value of *ps is left
       unspecified.

.SH Example


// Run this code

 #include <clocale>
 #include <cstring>
 #include <cwchar>
 #include <iostream>

 void print_mb(const char* ptr)
 {
     std::mbstate_t state = std::mbstate_t(); // initial state
     const char* end = ptr + std::strlen(ptr);
     int len;
     wchar_t wc;
     while ((len = std::mbrtowc(&wc, ptr, end-ptr, &state)) > 0)
     {
         std::wcout << "Next " << len << " bytes are the character " << wc << '\\n';
         ptr += len;
     }
 }

 int main()
 {
     std::setlocale(LC_ALL, "en_US.utf8");
     // UTF-8 narrow multibyte encoding
     const char* str = "z\\u00df\\u6c34\\U0001d10b"; // or u8"zß水𝄋"
                       // or "\\x7a\\xc3\\x9f\\xe6\\xb0\\xb4\\xf0\\x9d\\x84\\x8b";
     print_mb(str);
 }

.SH Output:

 Next 1 bytes are the character z
 Next 2 bytes are the character ß
 Next 3 bytes are the character 水
 Next 4 bytes are the character 𝄋

.SH See also

   mbtowc    converts the next multibyte character to wide character
             \fI(function)\fP
   wcrtomb   converts a wide character to its multibyte representation, given state
             \fI(function)\fP
   do_in     converts a string from ExternT to InternT, such as when reading from file
   \fB[virtual]\fP \fI\fI(virtual protected member function\fP of\fP
             std::codecvt<InternT,ExternT,StateT>)
   C documentation for
   mbrtowc
